Off-the-shelf CAR-T cell therapies for relapsed or refractory B-cell malignancies: latest update from ASH 2023 annual meeting

Abstract

Currently, many off-the-shelf chimeric antigen receptor (CAR)-T cell products are under investigation for the treatment of relapsed or refractory (R/R) B-cell neoplasms. Compared with autologous CAR-T cell therapy, off-the-shelf universal CAR-T cell therapies have many potential benefits, such as immediate accessibility for patients, stable quality due to industrialized manufacturing and additional infusions of CAR-T cells with different targets. However, critical challenges, including graft-versus-host disease and CAR-T cell elimination by the host immune system, still require extensive research. The most common technological approaches involve modifying healthy donor T cells via gene editing technology and altering different types of T cells. This article summarizes some of the latest data from preclinical and clinical studies of off-the-shelf CAR-T cell therapies in the treatment of R/R B-cell malignancies from the 2023 ASH Annual Meeting (ASH 2023).

To the editor

Off-the-shelf chimeric antigen receptor (CAR)-T cells can improve the availability of clinical treatments for patients with relapsed or refractory (R/R) B-cell malignancies by overcoming the limitations of inconsistent quality, high cost, long manufacturing cycles and occasional production failures. The proliferation, persistence and allogeneity of off-the-shelf CAR-T cells, as well as graft rejection by the host immune system, are the primary determinants of the safety and therapeutic effects of these treatments. The two fundamental methods for universal CAR-T cell production are the use of gene editing technology and the adoption of specific T-cell subtypes endowed with universality. We presented several recent studies on the use of off-the-shelf CAR-T cells for the treatment of R/R B-cell malignancies from the 2023 ASH Annual Meeting (ASH 2023).

Off-the-shelf CAR-T cell therapies based on gene editing

To reduce the risk of graft-versus-host disease (GVHD) and host-versus-graft reactions, knockout (KO) of the genes that encode the T cell receptor alpha (TCR) constant (TRAC) and CD52 by transcription activator-like effector nuclease (TALEN) technology in combination with an anti-CD52 antibody can be used to prevent TCR-mediated recognition of histocompatibility antigens and protect CAR-T cells from lymphodepletion (LD) mediated by an anti-CD52 antibody. [1,2,3]. Through the application of Cellectis' TALEN® technology, healthy donor T cells are manipulated to generate ALLO-501/ALLO-501A, which is an allogeneic anti-CD19 CAR-T cell line with TRAC and CD52 deletions (Table 1). ALLO-501/ALLO-501A infusions have shown favorable safety and efficacy in patients with R/R large B-cell lymphoma and follicular lymphoma. Twenty-four percent (20/87) of patients experienced cytokine release syndrome (CRS); grade 3–4 CRS and immune effector cell-associated neurotoxicity syndrome (ICANS) both occurred in 1% of patients (Table 2) [1]. There was no significant increase in the occurrence of adverse events associated with enhanced LD. Allogeneic UCART22 and UCART20X22 CAR-T cells were also developed using TALEN technology to disrupt the TRAC gene and CD52 gene. UCART22 Process 2 was administered to three patients with CD22-positive B-cell acute lymphoblastic leukemia (B-ALL), and two patients achieved minimal residual disease (MRD)-negative complete response (CR) without any severe CRS or ICANS [2]. One hundred percent (3/3) of patients with R/R lymphoma who received UCART20 × 22 had a response accompanied by grade 1–2 CRS; neither ICANS nor GVHD occurred. Notably, two patients who previously received anti-CD19 CAR-T-cell therapy achieved metabolic CR [3]. P-BCMA-ALLO1 is a piggyBac® transposon-generated allogeneic CAR-T cell-targeting B-cell maturation antigen (BCMA). The TCRβ 1 chain gene and the β-2 microglobulin gene (B2M) were disrupted by the Cas-CLOVER™ site-specific editing system [4]. The median time from enrollment to infusion was reduced to 7 days. Twenty-one percent (7/22) of patients experienced CRS of low severity, and one had grade 1 ICANS. The overall response rate (ORR) in arms P1 and P2 using optimized LD was 82%, and two patients in arm P2 reached stringent CR [4].

Table 1 Properties of off-the-shelf CAR-T cell therapies updated at ASH 2023

Table 2 Outcomes of clinical studies of off-the-shelf CAR-T cell therapies in relapsed or refractory B-cell malignancies

The reverse universal CAR platform (RevCAR), which targets CD19 and CD20, includes a universal CAR-T cell with KO of the genes encoding the TCR, human leukocyte antigen (HLA)-A and class II major histocompatibility complex transactivator gene (CIITA) and a soluble adaptor called the targeting module (R-TM19/20) [5]. This approaches induces better tumor clearance in B-ALL and lymphoma xenograft models even after CD19-negative relapse [5]. CRISPR-Cas12b is an RNA-guided nuclease platform for genome editing that contains a single RuvC nuclease domain without an HNH domain. It has been used to disrupt B2M, CIIA and TRAC to produce CD22-targeting hypoimmune CAR-T cells (SC262) due to its high efficiency and decreased off-target toxicity in human genome editing [6]. CD47-overexpresing SC262 cells were generated, and these cells can evade killing by NK cells and macrophages by triggering the CD47-SIRPα "don’t eat me" signaling pathway and ultimately elicit robust tumor control in vitro and in vivo [6].

In addition, a novel non-gene-editing strategy to generate ThisCART19A (TCRαβ/CD3 and/or HLA-I intracellular sequestered) was used to transduce a construct encoding a CD19 CAR and a KDEL-tagged anti-CD3 single-chain variable fragment (scFv) into T cells. The secretion of the TCRαβ/CD3 complex from the endoplasmic reticulum was prevented, resulting in the loss of TCR expression. A total of 25% (2/8) of patients with R/R B-ALL experienced grade 3–4 CRS, and 37.5% (3/8) of patients had ICANS, while encouraging efficacy profiles revealed that 100% (7/7) of patients had MRD-negative CR/CR with an incomplete hematologic recovery rate, and 57% (4/7) of patients remained in response with a median follow-up of more than 4.9 months [7].

Off-the-shelf CAR-T cell therapies originating from specific T-cell types

Epstein‒Barr virus-specific T cells (EBVSTs) can effectively eliminate EB virus-related tumor cells and are considered to be a potential off-the-shelf source due to their restricted TCR repertoire [8, 9]. The 19-28z CAR EBV-CTLs were EBVSTs that were modified with an anti-CD19 CD28-containing CAR and were administered to patients who relapsed or required consolidation therapy after allogeneic or hematopoietic stem cell transplantation [8]. Six percent (1/16) of these patients developed grade 1 CRS, and 18% (3/16) had skin GVHD, including 1 patient with grade 3 GVHD. The 3-year overall survival rate was 74% following multiple infusions. These T cells had lower expression of exhaustion markers, which may contribute to the promising long-term outcomes [8]. ATA3431, which carries a novel CD3ζ signaling domain, 1XX, to extend effector function, is a bispecific CD19- and CD20-targeting allogeneic CAR-T cell based on the EBVST platform that can reliably inhibit B-cell tumor growth according to preclinical evaluations [9].

CAR + γδT cells recognize and kill tumor cells via CAR-dependent and CAR-independent mechanisms, reducing tumor escape without the potential for GVHD. The CD20-targeted universal CAR + Vδ1 γδT cell line ADI-001 exhibited robust dose-dependent expansion and persistence in a phase I trial. Moreover, clinical responses were related to ADI-001 cellular kinetics, regardless of HLA mismatching [10]. Leong et al. altered Vγ9Vδ2 T cells with a reverse fate receptor so that they could avoid activation-induced cell death and augment cytokine signaling via the extracellular domain of Fas and linked intracellular MyD88 [11]. The armed Fas88/CD19.CAR-Vδ2 T cells mediated tumor elimination via massive amplification and persistence in NALM6-bearing mice, suggesting their potential for clinical translation [11]. Induced pluripotent stem (iPS) cells can self-renew, and iPS-derived cytotoxic T lymphocytes (iPS-rCTLs) are expected to survive long term and sustain their cytotoxicity in vivo. IPS-rCTLs transduced with an αCD38 CAR could suppress tumor growth and carry no risk of CD38-mediated fratricide [12]. Double-negative T cells (DNTs) are CD3-positive memory-like T cells that do not have HLA restriction owing to the absence of CD4 and CD8 expression. The first-in-class humanized anti-CD19 allogeneic DNT RJMty19 was well tolerated in 12 patients with non-Hodgkin's lymphoma, and grade 2 CRS was observed in 1 patient without any GVHD or ICANS. The ORR and disease control rate were 40% and 100%, respectively, at the highest dose [13].

Conclusion and further perspective

Overall, preclinical and clinical research on the use of universal, off-the-shelf CAR-T cells to treat R/R B-cell malignancies has been progressing rapidly, and these cells have demonstrated reliable safety profiles. Most allogeneic CAR-T cell therapies are barely superior to the approved autologous CAR-T cell therapies in terms of efficacy. Gene-editing strategies can transform allogeneic T cells into universal T cell sources through the disruption of critical genes related to allogeneity, such as TRAC, CIITA, and B2M. However, the impact of TCR disruption on the capacity of CAR-T cells to proliferate and kill tumors is still inconclusive. In addition, manufactured CAR-T cells derived from EBVSTs, iPS-rCTLs, γδT cells and DNTs usually equip off-the-shelf CAR-T cells with some inherent properties, including minimal alloreactivity and tumor cytotoxicity. With the increased accessibility and potency of CAR-T cell therapy, establishing platforms for clinical high-yield off-the-shelf CAR-T cell therapy is expected to provide patients with more standardized, dependable, and effective therapeutic approaches.